I've been working on this for a while now. I have these files:
main.c
zSim.h
zSim.c
zDynamicArray.h
zDynamicArray.c
zOptions.h
zOptions.c
zMain.h
zMain.c
All of the files and headers are located within the same folder.
My main has the following includes:
#include "zDynamicArray.h"
#include "zOptions.h"
#include "zMain.h"
#include "zSim.h"
#include <stdio.h>
#include <math.h>
I am using header guards. Just for example, this is from my zSim.h file:
#ifndef SIM_H
#define SIM_H
#include "zDynamicArray.h"
#include "zOptions.h"
//This Header is accountable
//for all Simulation Related things.
int Simulate(SIMOPT so,PRINTOPT po);
#endif
and this is a snippet from my zSim.c code (maybe I am doing something wrong here?):
#define M_PI 3.14159265358979323846
#include "zSim.h"
#include "zDynamicArray.h"
#include "zOptions.h"
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
I am compiling using this gcc command:
gcc main.c zSim.c zOptions.c zDynamicArray.c zMain.c -o TEST
and I also used:
cc -c main.c
cc -c zSim.c
cc -c ... etc
cc *.o -o TEST
They all result in an undefined reference for anything in the math.h library. Also when I use the gcc -I command, math is still undefined.
If i compile using gcc main.c, I get unresolved references for anything in my header files.
What should I do?
try ading -lm at the end : gcc -c main.c cc -c zSim.c cc -c ... etc cc *.o -o TEST -lm
You have to link the math library with the -lm option. The reason why is explained here : Why do you have to link the math library in C?
they all result in an undefined reference for anything in the math.h library
math.h is only the header file which contains prototypes and type declarations. You also need to link against the math library when creating your executable. Add -lm to your gcc call:
gcc main.c zSim.c zOptions.c zDynamicArray.c zMain.c -o TEST -lm
See also Undefined reference to `sin`.
Related
I'm pretty sure this is a simple question but I've searched online for about half an hour.
I have 3 files:
02_01.c
#include <stdio.h> // Notice the library included in the header of this file
#include <stdlib.h>
#include "myLibrary.h" // Notice that myLibrary.h uses different include syntax
#define MAX_LENGTH 21.8
#define WORK_WEEK 5
int main(void) {
function1();
return EXIT_SUCCESS;
}
myLibrary.c
void function1(void){
puts("It works :)");
}
void function2(void){
//This function does nothing as well
}
myLibrary.h
#ifndef MYLIBRARY_H_
#define MYLIBRARY_H_
void function1(void);
void function2(void);
#endif /* MYLIBRARY_H_ */
First, I navigate to my working directory.
Normally in a file with no local headers I would type:
gcc -o 02_01 02_01.c
./02_01
and it would work.
I've tried a variety of things like:
gcc -o 02_01 02_01.c myLibrary.c
which gives me an error "implicit declaration of function 'puts'
gcc -o myLibrary myLibrary.c which also gives the same error.
What should I be typing in the terminal in ubuntu?
So I'm assuming that the puts() function in myLibrary.c is not connected to 02_01.c which is where I include stdio.h.
You must include required headers in every file, where you using included functions. In your case, you must include #include <stdio.h> in beginning of your myLibrary.c file.
Also, you probably want to build .a library and link with it later.
So, finally:
Compile lib:
gcc -c -o mylib myLibrary.c
Make static lib:
ar rcs libMyLib.a mylib
Compile app and link together:
gcc -o 02_01 02_01.c -L. -lMyLib
I am having trouble with multiple definitions of functions. All other solutions here on stack overflow have not worked out for me.
This is my main.c:
#include "lib.h"
int main(){
test();
}
This is the lib.c file:
#include "lib.h"
int var;
void test(){
//code here
}
And this is the lib.h file:
#ifndef _HTTPLIB_H_
#define _HTTPLIB_H_
#include <stdio.h>
extern int var;
extern void test();
#endif
I have checked and there are no definitions of any function twice and I am never including a .c source file.
I am compiling with
gcc lib.c main.c -Wall -g -o main
main: In function 'test': (.text+0xfdd): multiple definition of 'test' /tmp/ccb8byZi.o:lib.c:(.text+0xef9): first defined here'
real code:
main file: http://pastebin.com/xr3DF0TE
lib.c and lib.h file: http://pastebin.com/KemhKX3f
This is the compilation code
gcc -lpthread -D_REENTRANT httplib.c http.c -o -g http
real error message:
http: In function `sigusr1':(.text+0xfdd): multiple definition of `sigusr1'/tmp/ccb8byZi.o:httplib.c:(.text+0xef9): first defined here
gcc -lpthread -D_REENTRANT httplib.c http.c -o -g http
Here's your problem: You're telling gcc to compile 3 files (httplib.c, http.c, http) into an executable called -g. This is because the argument after -o is taken to be the output filename.
The errors are caused by you apparently having an http executable lying around, which already contains the (compiled) functions defined in httplib.c.
Fix:
gcc -lpthread -D_REENTRANT httplib.c http.c -g -o http
I have a problem with message queues in C in Ubuntu. I use VirtualBox to run the Ubuntu.
I took error which is "undefined reference to mq_open. ld returned 1 exit status".
I know there is a same question as this but I tried that solution but it did not worked, so I want to ask again. Please help!
Here is my code, it is really simple but I can not even compile it.
this is my deneme.c
#include <stdlib.h>
#include <mqueue.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include "sharedMsg.h"
int main()
{
mqd_t mq;
mq = mq_open(MQNAME, O_RDWR | O_CREAT, 0666, NULL);
}
this is my sharedMsg.h
struct item{
char *word;
int lineNum;
};
#define MQNAME "/sentmsg"
and finally this is my MakeFile
all: deneme
deneme: deneme.c
gcc -g -Wall -o deneme deneme.c -lrt
clean:
rm -fr *~ *.o
The problem with your Makefile is that your all target depends on demene but the target that specifies -lrt is called demene1. Thus, the default inference rules kick in and demene is attempted to be linked without -lrt. The rule for deneme1 is also wrong in that it attempts to create a binary named deneme, even though the rule should create deneme1. To resolve this, change the first to third lines to
all: deneme1
deneme1: deneme.c
gcc -g -Wall -o deneme1 deneme.c -lrt
or the second line to
deneme: deneme.c
(Note: The OP has edited the question and fixed the Makefile after this answer)
You have a broken Makefile.
The reason why you've even seen the linker error is that you have probably executed make deneme. In that case make will try to compile dename.c with default compiler options (because it did not find a target called deneme) and the default options do not include -lrt.
You have to fix your Makefile (replace deneme1: with deneme:)
all: deneme
deneme: deneme.c
gcc -g -Wall -o deneme deneme.c -lrt
clean:
rm -f deneme *~ *.o
I have writting this code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netinet/in.h>
#include <linux/types.h>
#include <linux/netfilter.h>
#include <libnetfilter_queue/libnetfilter_queue.h>
int main(int argc, char **argv)
{
struct nfq_handle *h;
printf("opening library handle\n");
h = nfq_open();
nfq_close(h);
exit(0);
}
and when I try to compile it says that:
/tmp/ccEv9MYS.o: In function `main':
test1.c:(.text+0x1a): undefined reference to `nfq_open'
test1.c:(.text+0x2a): undefined reference to `nfq_close'
collect2: ld returned 1 exit status
I tried checking if the library is found by gcc and it is (when I modifiy the incluse of libnetfilter_queue there is an error), I recompiled the library and made sur that the fonctions I'm calling are in in it.
If you have any clue thanks for helping
Icompile using this:
gcc -o test test1.c
I have also tried:
gcc -o test -lnetfilter_queue test1.c
gcc -o test -L/usr/local/lib test1.c
Well, from the gcc manual page, for the -llibrary linking option
It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, ‘foo.o -lz bar.o’ searches library ‘z’ after file foo.o but before bar.o. If bar.o refers to functions in ‘z’, those functions may not be loaded.
That says, the linker works from left to right, so need to put the dependent on left hand side.
You need to change your compilation statement to
gcc -o test test1.c -lnetfilter_queue
How can I include foo() function of foo.c in this small program (sorry for my noob question):
In my foo.h file:
/* foo.h */
#include <stdio.h>
#include <stdlib.h>
int foo(double largeur);
In foo.c:
/* foo.c */
#include <stdio.h>
#include <stdlib.h>
#include "foo.h"
int foo(double largeur)
{
printf("foo");
return 0;
}
And in main.c:
/* main.c */
#include <stdio.h>
#include <stdlib.h>
#include "foo.h"
int main(int argc, char *argv[])
{
printf("Avant...");
foo(2);
printf("Apres...");
return 0;
}
After compiling:
$ gcc -Wall -o main main.c
I get this error:
Undefined symbols: "_foo",
referenced from:
_main in ccerSyBF.o ld: symbol(s) not found collect2: ld
returned 1 exit status
Thanks for any help.
$ gcc -Wall -o main main.c foo.c
GCC doesn't know to look for foo.c if you don't tell it to :)
Creating a program in C requires two steps, compiling and linking. To just run the compiling part, use the -c option to gcc:
gcc -c main.c
This creates an object file, main.o (or main.obj on Windows). Similarly for gcc -c foo.c. You won't get the error message above at this stage. Then you link these two object files together. At this stage, the symbol foo is resolved. The reason you got the error message was because the linker couldn't find the symbol, because it was only looking at main.o and not foo.o. The linker is usually run from gcc, so to link your object files and create the final executable file main, use
gcc -o main main.o foo.o
You have to compile foo.c also because it is another module. Let me see how they do it in gcc:
$ gcc -Wall main.c foo.c -o main
You could also do this in your MakeFiles, like this:
APP_NAME = Foo
Foo_HEADERS = foo.h
Foo_FILES = main.c foo.c
If you're not so much familiar with MakeFiles i suggest you to take a look at Make Docs, but this is a simple example, APP_NAME sets the name of the compiled executable(in this case is Foo), Foo_HEADERS will set the headers used by your application, Foo_FILES you will set the source files of your applications, remember to put the APP_NAME(in this case Foo) at the beginning of _HEADERS and _FILES. I suggest you to use MakeFiles because they will organize you application build process and will be better for the end-user.